libsel4vka: make invalid object type errors non-fatal

pragma once and for all

Fix licenses

libsel4vka: Refactor object and kobject definitions

Primarily this change allows x86 object and kobject definitions to be
futher abstracted by the current sel4_arch. To achieve this some
additional arch abstractions are done, resulting in minor changes
to the arm definitions.

In the process various cleanup to remove #ifdef blocks has also
been done.